#include <iostream>
using std::endl;
using std::cout;
using std::string;

void test1(){
    string str1="hello";
    string str2="world";
    string str3=str1+str2;

    
    cout <<str3<<endl;
    const char *cstring=str3.c_str();
    cout<<cstring<<endl;
}
int main(int argc, char * argv[]){
    test1();
    cout<<"hello world"<<endl;
    return 0;
}

